Did I screw up, or am I missing something in the science?

[Bogie]

Just caught part of a commercial that was talking about how the average commuter spewed 3.5 tons (that's 7,000 pounds, last I looked) of carbon into the atmosphere every year...

Now...

Assume I drive 12000 miles/year, and my car gets 30mpg
 
It uses 400 gallons of gas.

Not sure what regular gas weighs, but avgas runs about 6 pounds/gallon.

So that's 2400 pounds. Before any energy is released.

Now, either such folks as Einstein and Hawking were hugely delusional, or someone's lying to us.

[yesitsloaded]

I would assume they are counting tractor trailer rigs in that equation which screws up the numbers of both miles traveled and MPG. Considering the SUV craze and the older cars on the road I would bet the average MPG is closer to 20 than 30.

[Gewehr98]

Don't people also exhale carbon dioxide? 

It ain't all about the cow farts...

[Nitrogen]

I've seen differing numbers for the amount of carbon that gets put in the atmosphere from burning a gallon of gas, from 20lbs to 35 lbs.  For arguments sake, I'll pick the lowest number I found, 20lbs.

Average MPG is about 24 for passanger cars, so let's use that number for the heck of it.

Also, assuming 12,000 miles a year:

That means 500 gallons of gas a year.
That means you put 12500 lbs of carbon into the atmosphere, or 5 tons.

So yeah, they are lying to you.  It's worse.

here's how esurance came up with their numbers after digging:

Vehicle Emissions

To estimate auto emissions, the calculator divides the average number of miles an American drives in a year (12,000 Miles) [US Environmental Protection Agency, Office of Transportation and Air Quality, "Emission Facts: Greenhouse Gas Emissions for Typical Passenger Vehicle," February 2005] by the estimated fuel efficiency (21 mpg) of the average American vehicle. This amount is multiplied by 19.564 [U.S. Department of Energy and the Energy Information Administration, Instructions for Form EIA 1605B, Voluntary Reporting of Greenhouse Gas Emissions] the amount of pounds of carbon dioxide that is emitted as a result of burning one gallon of gasoline. To calculate metric tons, this number is divided by 2,205.

I got this from here:

http://www.earthlab.com/carbon-calculator.html
which esurance linked to.
(I'm assuming that's the commercial you meant.)

[Bogie]

How does burning something that weighs 6 pounds create 20 pounds of waste?
 

[Sindawe]

"Emission Facts: Greenhouse Gas Emissions for Typical Passenger Vehicle," February 2005] by the estimated fuel efficiency (21 mpg) of the average American vehicle. This amount is multiplied by 19.564 [U.S. Department of Energy and the Energy Information Administration, Instructions for Form EIA 1605B, Voluntary Reporting of Greenhouse Gas Emissions] the amount of pounds of carbon dioxide that is emitted as a result of burning one gallon of gasoline.

WHAT? /incredulous

So combustion of one gallon of gasoline, which weighs ~6.1 pounds/gallon (1) will produce close to 20 pounds of carbon dioxide?

Well, I guess its close enough for government work. : rolleyes :

Its been a while since I've worked through these types of problems, but here goes.

500 gallons = 1,892.70 liters

Combustion of 1 liter of gasoline generates 52.8 moles of CO2 (2)

So burning 1,892.70 L of gasoline will generate 99,934.56 moles of CO2. If 1 mole of CO2 has a mass of 0.044 kg, that works out to 4397.12 kg of CO2.  At ~2.2 pounds per kg, that is about 9673.66 pounds of CO2

[Bogie]

Uh...

So something that weighs 3,000 pounds (give or take a little) can actually produce 9,000+ pounds of waste?
 
Sin, has Jeff killed anything lately? I've checked a few times, and not seen any updates. Is the Scourge of Songbirds doing okay?

[Nitrogen]

How does burning something that weighs 6 pounds create 20 pounds of waste?

Science!
Let me try and explain it.  It's been a while since I did chemestry, so hopefully I get this right:

Most of that comes from the Oxygen in the air already.

Basically, when gasoline burns, the hydrogen and Carbon in the gasoline is broken apart to create energy.
The hydrogen combines with Oxygen to form water (H2O of course) and the carbon combines with oxygen to form Carbon Dioxide.

Carbon atoms have an atomic weight of 12, and Oxygen atoms have an atomic weight of 16, making CO2 weighing 44.

Gas is 13 percent hydrogen and 87 percent carbon.  The carbon in a gallon of gasoline weighs 5.5 lbs.

Now, lets figure out how much the oxygen that will become part of the CO2 weighs:
Carbon Dioxide=44
Carbon = 12
Oxygen= 16
so 44/12= 3.7

so 3.7 * 5.5 =20.35

Make sense?  I hope so.

In simple terms, the carbon and hydrogen are broken apart.  The hydrogen is discarded, bonding with Oxygen to make harmless water.  The Carbon bonds with oxygen in the air.

Let's assume that all gasoline is Octane. (its not always.)
Octane is C8H18
you already know you need Oxygen to burn, thats where the oxygen comes from.

Ideally, when gasoline burns, you'll make eight molecules of carbon dioxide (CO2) and nine molecules of water (H2O). The eight molecules of CO2 weigh about three times more than the one molecule of octane you started with.

That doesn't mean you've violated the law of conservation of mass; instead, you've added the weight of the oxygen from the air to the weight of the carbon from the gasoline.

Now, this is in perfection.  Perfection doesn't always happen.  If you don't have enough oxygen, you'll create Carbon Monoxide instead, as well as other garbage that causes ozone, etc.

EDIT:  It's late and I fixed my figures, and added a better explanation.  (I hope.)

[charby]

Bogie does your head hurt?

-C

[Bogie]

It's like a perpetual stuff machine.
 
BTW, finally found a substrate that doesn't look all that bad for the clings. Still not all that happy with 'em, so you're getting extras...
 

[Len Budney]

How does burning something that weighs 6 pounds create 20 pounds of waste?

I can't vouch for their numbers, but burning also takes oxygen from the air. Its weight also needs to be considered. Possibly other ingredients as well, since I don't know the details of the chemistry of car exhaust. Nitrogen's calculation looks in the ballpark.

Yesitsloaded is also right, they're not just talking about your car. Trucks, etc., produce much more waste than you do.

--Len.

[charby]

It's like a perpetual stuff machine.
 
BTW, finally found a substrate that doesn't look all that bad for the clings. Still not all that happy with 'em, so you're getting extras...
 

I wondered where they were at.   

[cassandra and sara's daddy]

do they also figure the carbon impact from refining and transporting the fuel in there

[Nitrogen]

do they also figure the carbon impact from refining and transporting the fuel in there

No.  This is just the carbon impact for burning it.  I don't know much about how gasoline is refined outside of the chemistry involved, so I can't speak to the carbon impact of refinement. From what I know, the actual refinement is a zero-sum game, but the external bits reuqired to refine must have a carbon impact, I ust dont know what it'd be. (heat required, electricity,etc.)

[X Who]

Just caught part of a commercial that was talking about how the average commuter spewed 3.5 tons (that's 7,000 pounds, last I looked) of carbon into the atmosphere every year...

Am I missing something?  This says CARBON, not CO2.  Is the assumption that this is a mis-quote?

[drewtam]

This says CARBON, not CO2.  Is the assumption that this is a mis-quote?

Yes.

[charby]

carbon emissions are know as CO2 and CO mostly CO2

That is why they are talking about carbon building by planting trees to absorb the CO2 and releasing O2 and using the carbon in their building blocks of growth.

[drewtam]

That is why they are talking about carbon building by planting trees to absorb the CO2 and releasing O2 and using the carbon in their building blocks of growth.

Then we should cut down those trees and treat them so they don't rot. And plant more in their place. That way it'll be a huge carbon sink. Now that we have all this treated wood, we should do something with it, like cutting it into little pieces 2" by 4" and 12' long. Also, by clearing small strips of woods we should be able to prevent forest fires and other disasters in places like California and our national forests.

I am now taking donations from smucks globally conscious individuals to store and handle this carbon sink on my property. I charge a nominal fee of $3/pc. Remember, its for the future of our children.

Drew

[MechAg94]

If they actually used only the carbon weight, the numbers would make more sense, but not have the same impact on the public.  Propaganda before truth. 

[Gewehr98]

Drewtam, I like your way of thinking.

I'll add that we need to get the human population back down to what it was around the Little Ice Age, so that the exhalation CO2 emissions of several billion humans would be eliminated.

Soylent Green would help alleviate the hunger problem, too.   

[Matthew Carberry]

Drewtam, I like your way of thinking.

I'll add that we need to get the human population back down to what it was around the Little Ice Age, so that the exhalation CO2 emissions of several billion humans would be eliminated.

Soylent Green would help alleviate the hunger problem, too.   

Okay, I can see Soylent Green helping feed the hungry, but how will it help alleviate the population problem? 

[Bogie]

Well, getting into the science thing a wee little bit, but from what I understand, an acre of grassland, properly watered and fertilized, processes CO2 and produces a heckuvalotmore 02 than an acre of trees... And especially a lot more than an acre of rotting rain forest...
 

[Finch]

SOYLENT GREEN IS MADE OF PEOPLE!!!!




Ahem....

[Len Budney]

Well, getting into the science thing a wee little bit, but from what I understand, an acre of grassland, properly watered and fertilized, processes CO2 and produces a heckuvalotmore 02 than an acre of trees... And especially a lot more than an acre of rotting rain forest...

Absolutely right. And an acre of corn produces WAAAY more O2. Trees aren't nearly as magical as the enviros claim.

--Len.

[griz]

Then we should cut down those trees and treat them so they don't rot. And plant more in their place. That way it'll be a huge carbon sink.

That's the part of the math I don't understand.  If I cut down 1000 trees to plant corn to turn into biofuel, do I have to plant 10,000 trees to make up for the ones I cut down or do I get 10,000 carbon credits because of I made fuel to use in hauling the trees away?  Do you get more credits if you vote for Democrates instead of Republicans?